Op we need answers tk the questions but even so, are they his children?.
Did he want children because at the moment he sounds like a stupid git. It sounds like he doesn't value or like his dc and is un connected to them.
Most of us love our dc and want to show him them a good time which yes, of course comes from walks, and playing and free stuff but with the occasional treat!
He sounds like he doesn't care for them at all, does he have other plans to actually run away on his own?
We had v small inheritance as well and I used well under a grand to buy annual pass to theme park. It was fabulous.
Everything else in pension and saving.
The family isn't just about him and his goal and desires its also about his children and what they need and want right now.
Tbh our weekly fun budget isn't that much more op but we divide all our ££ up into petrol, fun, christmas and have small saving pots on the go all the time.
Maybe if he did this (assuming he does actually love you all) it would ease his worries over £ because he knows x is for frivolity but y has been put aside for serious stuff.?
We have lots of cash allocated even down to petrol etc. I have also got a fun 'extra' pit going. So today we have family day out, we didn't use our weekend fun money but to top that up, I have an extra 40 from our fun extra pot, specially saved for such occasions😂😇.
Dh used to stress about ££ but breaking things down like this has helped, ring fencing all our needs. Of course it wouldn't work if the only project and need however was putting all money away for him.
You need to get to the bottom of this, and sort out money for everyone in family.